You are overestimating how technical most folks are. I know kids and older adults, on either side of my age, that have no concept of a filesystem, a URL, an APK to download, things like that, because they've never needed any of that.

Attention is finite.

Hence, web app's aren't really blocked by iOS/Android, but that's still a basically insurmountable hurdle simply because it's not the usual procedure for operating a phone. Defaults and accessibility are king (and Apple/Google know it).